I'm sure I've heard the Duke's version, but I most remember Red Skelton's. Man oh man. Powerful.
http://www.youtube.com/watch?v=yQM1oLnMLNU
John Wayne: “America - Why I Love Her”
http://www.youtube.com/watch?v=3Jf3MQpffBc
John Wayne and the Pledge of Allegiance
http://www.youtube.com/watch?v=_nMzqAzIsxc
John Wayne: “Face the Flag”